Abstract: Plant water use efficiency（water use Efficiency，WUE）varies with environmental conditions and peaks during the“golden hour”（GH）. During this time，plants were able to produce more dry matter with the consumption of less water. The traits related to WUE at the golden hours were referred to as“golden WUE”traits（GHW）. This study used a WUE model to derive that canopy conductance，the ratio of transpiration rate to saturation vapor pressure deficit，can be used to infer photosynthetic rate，and was confirmed through conventional measurements of low-flux canopy gas exchange parameters. A method based on high-throughput physiological phenotyping to define GHW traits were developed. This method uses cumulative canopy conductance during the GHW period（AccGHW），the proportion of AccGHW to the entire day（fGHW），and estimated WUE（WUEe）as the comprehensive quantification parameters. Using this method，24 varieties of common bean（Phaseolus vulgaris L.）collected from the globe and successfully identified a set of elite/poor lines were screened.

Key words: water use efficiency, golden hour, canopy conductance, common bean, natural variation, water–saving and yield balance